The present invention relates to an electronic device for selecting and controlling the steering modes of vehicles, in particular industrial vehicles with four steering wheels.
It is known that the four steering wheels of an industrial vehicle can be positioned in various ways, by the operator, in order to align them according to three main modes of vehicle steering: normal or road steering, the mode known as xe2x80x9cat pilgrim stepxe2x80x9d or xe2x80x9ccoordinatedxe2x80x9d and the mode known as xe2x80x9ccrabxe2x80x9d.
The compulsory condition for correct operation of switching from one mode to the other lies in the fact that the axles of the wheels must always be synchronised, meaning that the two centres of gravity of each axle must remain aligned along a direction perpendicular to the axle.
Therefore, at present, in order to change the steering mode, the operator must turn the steering wheel until identifying first the centre of the steered axle of the rear wheels and then switch to normal to centre the front wheels so that the centres of the two steered axles, rear and front respectively, are aligned along a direction perpendicular to the axles; only after this alignment operation, it is possible to switch to a desired steering mode.
Therefore, operations to identify and align the centres of each steering axle are performed, in the known way, by means of pilot lights, each of them flashing when the condition of synchronisation of each axle is complied with.
Thus, in order to change the steering mode, at present, the operator firstly must turn the steering wheel until a first pilot light of the instrument panel is on to indicate that the axle of the rear wheels is synchronised and then said operator must switch the steering mode of the wheels to the desired mode, by means of a switch or selector, also positioned on the instrument panel.
After the steering cylinder of the rear wheels has been locked, the operator must then turn the steering wheel again until reaching a position in which a second pilot light of the instrument panel, which identifies the position of synchronisation of the axle of the front wheels, is on; then it is possible to switch to another steering mode by using the selector.
It is evident that this procedure to vary the steering mode, although relatively simple to be performed by the operator of an industrial vehicle, however, requires extremely lengthy execution times, especially in the event that variations of the steering mode are particularly frequent (due, for example, to frequent variations in the structure of the ground or to the variety of routes to be taken by the vehicle).
Moreover, if there is an oil leak in the hydraulic distribution circuit or a blow-by from one chamber to the other of a steering cylinder, this causes loss of synchronism and alignment between the steering axles, which can no longer be retrieved except by performing a new alignment operation.
Lastly, the correct operation of these systems, in order to vary the steering mode, is closely dependent on the type of control and the manoeuvring ability of the operator, with consequent risks of erroneous steering geometries.
The object of the present invention is, therefore, to remedy the above inconveniences and, in particular, to indicate an electronic device for selecting and controlling the steering modes of vehicles, in particular industrial vehicles with four steering wheels, which permits all possible switchings from one steering mode to the other of the front and/or rear wheels of a vehicle to be performed automatically and in relatively short times, compared to the prior art.
Another object of the present invention is to indicate an electronic device for selecting and controlling the steering modes of industrial vehicles with four steering wheels, which permits easy and rapid retrieval of the synchronism between the front and rear axles, once said synchronism has been lost due to errors by the operator, malfunctions or leaks in the hydraulic distribution circuit.
A further object of the invention is to produce an electronic device for selecting and controlling the steering modes of industrial vehicles with four steering wheels, simple to use, even by operators who are not particularly skilled in traditional manoeuvres to synchronise the steering axles.
These and other objects are obtained by an electronic device for selecting and controlling the steering modes of vehicles, in particular industrial vehicles with four steering wheels, according to claim 1.
Other characteristics of the device can be deduced in the subsequent claims.
Advantageously, the electronic device according to the invention allows the operator to switch, automatically and by means of simple selection operations, to a desired steering mode, from any initial steering mode.
Moreover, switching to the steering mode requested takes place when the pairs of wheels mounted on the front and rear steering axles are perfectly synchronised.